Prognostic Meteorological Discussion
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000
FXAK02 KWNH 221856
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 PM EST SUN JAN 22 2017

VALID 12Z THU JAN 26 2017 - 12Z MON JAN 30 2017

...AN ACTIVE PRECIPITATION PATTERN WILL CONTINUE FROM
SOUTH-CENTRAL TO SOUTHEASTERN AK DURING THE PERIOD...


PERSISTENT RIDGING ALONG WESTERN NORTH AMERICA WILL MAINTAIN
LONGWAVE TROUGHING UPSTREAM FROM THE BERING SEA TO THE GULF OF AK.
A NUMBER OF EMBEDDED SHORTWAVES WILL CONTINUE TO TRANSLATE
EASTWARD WITHIN THIS ACTIVE CASCADE OF SYSTEMS. MANY OF THESE
FEATURES MAY LEAD TO DEEP SURFACE WAVES ACROSS THE REGION WITH
CONFIDENCE IN ANY ONE OF THESE CYCLONES ON THE LOWER SIDE. FOR
INSTANCE...ON THURSDAY MORNING...THE 00Z ECMWF/UKMET BOTH HAVE A
SUB-970 MB LOW ACROSS THE BERING SEA WHICH THE RECENT GFS RUNS
HAVE TENDED TO DOWNPLAY. LATER ON...A MORE PRONOUNCED SHORTWAVE
SWEEPS ACROSS THE NORTHEASTERN PACIFIC WHICH LIFTS A COMPACT
SURFACE WAVE UP TOWARD SOUTH-CENTRAL AK. THERE IS SOME LATERAL
SPREAD WITH THIS SYSTEM BUT THIS IS TO BE EXPECTED 5 TO 6 DAYS
OUT. TOWARD THE LATTER HALF OF THE FORECAST...AN IMPRESSIVE
LONGWAVE TROUGH EMERGES OUT OF SIBERIA BRINGING MARKED HEIGHT
FALLS FROM THE KAMCHATKA PENINSULA TOWARD THE BERING SEA. THE GFS
CONTINUES TO BE DEEPER WITH THIS SYSTEM WITH SUPPORT FROM ITS
ENSEMBLES.

OVERALL...AFTER COORDINATION WITH WFO ANCHORAGE...FELT A
COMBINATION OF THE 12Z GFS/00Z ECMWF WAS REASONABLE EARLY ON WITH
A SLIGHT PREFERENCE TOWARD THE 12Z GFS GIVEN A BETTER HANDLING OF
THE DAY 5 LOW MOVING INTO THE GULF OF AK. THEREAFTER...A THREE-WAY
BLEND OF ENSEMBLES...LED BY THE 06Z GEFS MEAN WAS UTILIZED IN
CONJUNCTION WITH THE 00Z ECMWF/NAEFS ENSEMBLE MEANS. IN TERMS OF
THE SENSIBLE WEATHER...AN ACTIVE STORM TRACK ACROSS THE ALEUTIANS
AND GULF OF AK WILL FAVOR MORE PRECIPITATION OVER SOUTH-CENTRAL TO
SOUTHEASTERN AK. TEMPERATURES SHOULD REMAIN ON THE MILDER SIDE
AFTER A COLDER PERIOD THE PAST WEEK OR SO. EVENTUALLY IT SHOULD
COOL OFF OVER NORTHERN AK IN RESPONSE TO THE DEEPENING UPPER
TROUGH EMERGING OUT OF THE BERING SEA.


RUBIN-OSTER

$$




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